Advise needed for Charity project

[bat]

I have been a long time reader on this forum and several years ago was an avid RC Helicopter hobbyist.

I have a neighbor who is in her 50's and has been un/underemployed for several years. She is working a base level job trying to make ends meet and keeps getting screwed by the lack of reliable public transportation in Columbus Ohio. She has to travel five miles to get to work. I Have an extra bike that I would like to turn into an electric bike for her to use to commute back and forth to work. I expect that with her age and weight she will probably need the batteries to power most of the trip. Since I am giving this away I would like to build something sub $400 if possible.

Requirements 12 mile real world range mix flat/hills
motor not higher than 750W

Thank you all for your wisdom
Tommy

 

[wesnewell]

Welcome to ES****Do this before your first post or now (it's retroactive)*****
Please go to the User Control Panel, select Profile, and then enter your city, state/province, and country into the Location field (country minimum) and save it. Once done, your location will appear in every post so you won't have people asking where you are ever again. This will help people help you. Example: Wylie, TX, USA. or just USA, but country as a minimum, and country is the most important. There are many cities with the same name all over the world. Without knowing what country you are in it's hard to make any recommendations. Thank you.

One of the best motor deals around.
http://www.ebay.com/itm/48V1000W-26-Rear-Wheel-Electric-Bicycle-LCD-Display-Motor-Kit-E-Bike-Conversion-/371135902750
But then you need a battery pack and charger. You need about 400 usable wh of battery and that's going to be hard to do for $145. So you'll be ~$100 short.

 

[bat]

Thanks Wesnewell,

Am I correct that a 400W battery would be around a 48V 10ah battery pack?
I assume the only way to get close to a pack like that for around $200 is to build one?
If so what cells or battery type would I need to plan on working with?
Just a point in the right direction. I'll do the searching and reading if a DIY battery project is what I need to do.
Thanks,
Tommy

 

[dogman dan]

She won't need 30 mph I bet, not for just 6 miles or so. So get her a yes kit, but the less powerful one. A 36v 12 ah lead pack will get her 6 miles reliably, and last awhile. But she'd need to charge to get home. 18 ah lead batteries would go both ways fine, but weigh a lot.

1 ah per mile is what she will need to go 20-25 mph using 36v. 400-500wh. This estimate includes a reserve she'll only use when it's windy. But the problem is, you can't pull 12 ah from 12 ah lead without ruining them.

Riding 15 mph will really help, if all you can afford is some 12 ah lead. At 15 mph, with brisk pedaling you will make it on 6-8 ah used.

 

[bat]

Thanks Dogman.
I am pretty sure she will not have access to charge her bike at her employer. Also do you have a link for a "yes kit" I have tried multiple searches on here and google and can not find the kit you are talking about. Yes is a terrible name for a product, it lacks distinction.
Tommy

 

[wesnewell]

The kit I linked is the newer 48V 1000W yescomusa kit. They sell cheaper on ebay than on their website.
http://www.yescomusa.com/Electric_Bicycle_Engine/
I wouldn't give my worst enemy a lead battery pack. Well, maybe I would if I really wanted them to suffer.
A 10ah 12s lipo pack with a bms will cost ~$200 and and would give her 20 miles @ 20 mph and a top speed of ~ 28mph. That's about the cheapest you can get out with a decent battery pack.

 

[bat]

That is doable,
now I just need to find the $200 battery pack with BMS. Or do I need to build it?

 

[wesnewell]

You will have to build it yourself, but it's easy using rc lipo. You need 6 of these.
http://www.hobbyking.com/hobbyking/store/__18631__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack_USA_Warehouse_.html
And then a 12s bms like or similar to this.
http://www.bmsbattery.com/smart/330-lifepo4lithium-ion-smart-bms-for-513-cells-in-series.html
select 20-40A option and 12s lipo.
And a charger set for 50.4V.
http://www.bmsbattery.com/18-alloy-shell
The 240W will charge the pack in ~2 hours.

 

[bat]

Thanks wesnewell!

 

[bat]

With the lipos you recommend that would make a 12s2p setup. Will I need 2 bms boards? also do I need a controller? I have been looking around for some good digrams on how to wire everything together. Also in my search I have seen a lot of bad press on the reliability of lipos. Do the BMS board pretty much tame these lipos to the point a non hobbiest could use them? I don't want my neighbor to get burnt up.

 

[anon0973923]

With the lipos you recommend that would make a 12s2p setup. Will I need 2 bms boards? also do I need a controller? I have been looking around for some good digrams on how to wire everything together. Also in my search I have seen a lot of bad press on the reliability of lipos. Do the BMS board pretty much tame these lipos to the point a non hobbiest could use them? I don't want my neighbor to get burnt up.

Paralleled batteries just act like one big battery so you'll only need a single BMS. You'll have to parallel the balance leads from each 12s battery. probably easiest to buy 2 prefab 2x6s parallel balance wires, file off the tabs and connect them side by side. Controller will come with the kit.

 

[wesnewell]

You just need 1 12s bms. The controller and everything else you need for the motor comes with the hub motor kit. I've been using rc lipo for years without a bms and never had a problem. I suggested a bms for 2 reasons. It offers good protection from over charging and it makes charging simple. And it's also the cheapest way to get a powerful battery that you don't have to worry about the weak C rates of other chemistries. RC lipo gets a lot of bad press because there are idiots out there that do crazy stuff with it. Any battery is only as safe as the person using it. And while it's not as safe as some other chemistries, you won't find a more powerful battery. And it will take a lot of abuse before causing a problem in most cases. See this abuse test.
http://endless-sphere.com/forums/viewtopic.php?f=14&t=27241
More info;
http://batteryuniversity.com/learn/article/types_of_lithium_ion
http://www.rchelicopterfun.com/rc-lipo-batteries.html
http://scriptasylum.com/rc_speed/lipo.html
To parallel the 4s battery packs, get 3 of these.
http://www.hobbyking.com/hobbyking/store/__32037__JST_XH_Parallel_Balance_Lead_4S_250mm_2xJST_XH_.html

 

[misterb]

You will have to build it yourself, but it's easy using rc lipo. You need 6 of these.
http://www.hobbyking.com/hobbyking/store/__18631__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack_USA_Warehouse_.html
And then a 12s bms like or similar to this.
http://www.bmsbattery.com/smart/330-lifepo4lithium-ion-smart-bms-for-513-cells-in-series.html
select 20-40A option and 12s lipo.
And a charger set for 50.4V.
http://www.bmsbattery.com/18-alloy-shell
The 240W will charge the pack in ~2 hours.

The BMS requires 2 additional fields when ordering:

overvolt protection:
undervolt protection:

what do you recommend here for a 12s?

 

[dnmun]

this is gonna be the very worst of worst recommendations from him.

a totally inexperienced middle aged woman with no idea of the risks of using lipo with no oversight to protect her and her house. what will he think of next.

 

[wesnewell]

The BMS requires 2 additional fields when ordering:

overvolt protection:
undervolt protection:

what do you recommend here for a 12s?

OVP 4.2V per cell
UVP 3.3V per cell
The 48V controller LVC should be 42V, so it should cut off the motor before a bms cell reaches 3.3V, assuming a pack in good condition.